Conversion circuit, system and method of executing an electrochemical process

ABSTRACT

A conversion circuit for converting an alternating current into a feed current for an electrochemical process is provided with at least one supply terminal for supplying an alternating feed current, a rectifier circuit for rectifying a supplied alternating feed current, and an output stage for supplying the rectified current to a device in which the electrochemical process is taking place. The conversion circuit is further provided with an input stage connected between the supply terminals and rectifier circuit, which input stage, when in use, confers upon the conversion circuit a substantially reactive input impedance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of PCT/NL2004/000142 filed Feb. 25, 2004, which claims priority to Netherlands application No. 1022786 filed Feb. 26, 2003.

BACKGROUND

1. Technical Field

A conversion circuit for converting an alternating current into a feed current for an electrochemical process is disclosed. The conversion circuit comprises at least one supply terminal for supplying an alternating feed current, a rectifier circuit for rectifying a supplied alternating feed current, and an output stage for supplying the rectified current to a device in which the electrochemical process is taking place. A system for carrying out an electrochemical process is disclosed that is suitable for placing a device in which an electrochemical process is running and which comprises a disclosed conversion circuit. A method of carrying out an electrochemical process is also disclosed which use a disclosed conversion circuit.

2. Description of the Related Art

Examples of conversion circuits, systems and methods using conversion circuits are illustrated in GB 2 197 551. In said publication, a battery charger is described. This battery charger may be used for charging miniature batteries. When powered by the mains, the input impedance of the known battery charger is substantially resistive in nature. The known battery charger has an input stage having a capacitor connected in series between the rectifier circuit and the power supply terminals. In the known battery charger, the capacitor serves to bring about a voltage drop, so that the voltage across the terminals of the battery doesn't become too high.

A disadvantage of this apparatus is that the performance of the electrochemical process that takes place during charging the battery is slow.

SUMMARY OF THE DISCLOSURE

Therefore, a conversion circuit, a system for carrying out an electrochemical process and a method of carrying out a electrochemical process are disclosed that accelerate the electrochemical process thereby providing a relatively high level of efficiency.

This is achieved by a conversion circuit provided with an input stage connected between the supply terminals and rectifier circuit. The input stage, when in use, confers upon the conversion circuit a substantially reactive input impedance.

The conversion circuit, when in use, has an input impedance of which the reactive component is higher than the resistive component. By using such an input stage, it is possible to supply more power to the electrochemical process, without the apparent power uptake increasing appreciably. By using a reactive input impedance in combination with power supply from an alternating feed current, a pulsating power is supplied to the electrochemical process, because the electrical and magnetic component of the electromagnetic waves propagating through conductors in the conversion circuit are out of phase. The disclosed conversion circuit is based on the concept that by thus separating the two components, the charge carriers which are involved in the electrochemical process acquire a higher mobility. In this way, the efficiency of the electrochemical process, and thus its speed, increases.

Preferably, the input stage comprises at least one capacitor connected in series between the supply terminals and the rectifier circuit. Also, the input stage is preferably comprised of a capacitor bank, which comprises one or more capacitors connected in parallel.

In this manner, an almost purely reactive input impedance may be obtained, as a result of which the advantageous effects of the disclosed conversion circuit manifest themselves in an enhanced manner.

The supply terminals are suitable for connection of the conversion circuit to the mains network, amongst others.

If the disclosed conversion circuit is connected directly to the mains network, it is simple to use in many places. Therefore, no separate alternating current power source is needed.

According to another embodiment, a system for carrying out an electrochemical process is disclosed, which is suitable for placing a device in which an electrochemical process is running and which comprises a disclosed conversion circuit.

This system has the same advantageous effects as the conversion circuit disclosed above.

Preferably, the disclosed system is suitable for use of a device in which the electrochemical process is taking place that comprises a container for an electrolyte solution, wherein the system is provided with means for generating pressure waves in the electrolyte solution present in the container of a device placed in the system.

The pressure waves improve the transport of the charge carriers that are involved in the electrochemical process. Additionally, they ensure a rapid removal of gasses released in the electrochemical process, so that the concentration thereof in the electrolyte solution is lower. This enhances the operation of the disclosed conversion circuit, so that the electrochemical process executes faster. An additional effect is that any crystallised electrolyte dissolves again more rapidly. Thus, a regenerative effect is obtained that is particularly advantageous if the electrochemical process is taking place in a relatively cold environment or has previously run in the opposite direction, because crystallisation of the electrolyte occurs most often in those cases.

In a preferred embodiment, the system comprises a fluid bath, in which the container can be placed and is provided with a means for generating pressure waves in the fluid bath when filled with fluid.

This is a highly effective manner of transmitting pressure waves, as the impedance of the fluid and electrolyte solution are in the same range, so that more power is transmitted. Furthermore, the system is usable in combination with various containers, which may thus be adapted to the type of electrochemical process without detracting from their suitability for use in the disclosed system.

According to yet another embodiment a method of carrying out an electrochemical process is disclosed, wherein use is made of a disclosed conversion circuit. This method has the advantage of being of relatively short duration.

In a preferred embodiment, the method comprises having the electrochemical process take place in a container filled with an electrolyte solution, and generating pressure waves in the electrolyte solution present in the container.

The pressure waves improve the transport of the charge carriers involved in the electrochemical process. This enhances the operation of the disclosed conversion circuit, so that the electrochemical process runs faster. Preferably, the method comprises generating pressure waves having a frequency in the range of 20 kHz and higher.

It has been determined experimentally that the effect of the pressure waves is highest in the frequency range between 20 kHZ and 50 kHz. When using an electrolyte solution with water as a component, the range of 38 46 kHz and, within that range, 41 43 kHz in particular, is best. This is connected with the fact that the resonance frequency of water molecules lies at approximately 42 kHz.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed circuits, methods and systems will now be explained in further detail with reference to the accompanying drawings, wherein:

FIGS. 1A and 1B are schematic top and side plan views respectively of a disclosed system according to this disclosure; and

FIG. 2 is a circuit diagram of a disclosed conversion circuit.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The disclosed system of FIGS. 1A and 1B, comprises a conversion circuit and a vessel 2 filled with water 1 forming a fluid bath. In the fluid bath, an electrolysis device 3 has been placed. The electrolysis device 3 comprises a fluid container 4, with a duality of electrodes 5 therein, which are immersed in an electrolyte solution 6. The electrodes 5 are connected to positive and negative poles 7,8 of the electrolysis device 3.

The circuit is generally suitable for any type of electrochemical process. The example that is detailed herein concerns electrolysis, for example of a sodium chloride solution to win chlorine. In a preferred embodiment, the system forms part of the drive train of a vehicle. This drive train further comprises a power source for driving the vehicle, which power source uses the product of the electrolysis as a source of energy. The power source may for instance consist of an internal combustion engine or a Stirling-motor running on hydrogen, but also of a combination of fuel cells and one or more electric motors. A generator supplying the alternating supply current to the conversion circuit may consist of a dynamo and optionally be used to recoup energy when slowing down the vehicle. A disclosed system comprising of the generator for generating alternating current, disclosed conversion circuit, an electrochemical cell in which an electrochemical process is taking place and a power source using the product of the electrochemical process, provides an especially efficient and rapidly responding system for vehicle propulsion.

The disclosed circuit is, however, also suitable for charging batteries and accumulators. The circuit is even suitable for charging batteries of types that cannot be recharged with conventional charging apparatus, such as carbon batteries. The circuit is particularly suitable for recharging lead sulphate batteries, such as are used in cars and lorries, for instance. There, the problem occurs that through repeated overcharging and deep discharging (in combination with low temperatures), sulphate is deposited on the electrode plates, as a result of which the capacity of the accumulator decreases over its lifetime. By means of the disclosed system, this effect can be reversed and prevented.

In use, as shown in FIG. 13, the electrolysis device 3 is placed on a pedestal 9 in the vessel 2 filled with water 1, wherein the fluid level is set such that the poles 7,8 just surface above the water 3. The poles 7,8 are connected to leads 10,11 (FIG. 1A), or another example by means of alligator clips (not shown) or other suitable connection means. The electronics of the disclosed conversion circuit, as shown schematically in FIG. 2, are accommodated in a housing 12. Thus, the disclosed system in this example comprises the conversion circuit, the housing 12 with the electronics accommodated therein, and the fluid bath, of which the function will be described in greater detail below.

The conversion circuit is preferably powered from the mains, although another source of alternating current could be used in principle, which in the context of this disclosure should also be taken to mean sources of polyphase current (three-phase current), such as a power current network. An example of a suitable source is an alternating current generator such as a car dynamo or an emergency backup power generator. It would also be possible to use a source of direct current coupled to a converter for converting the direct current into an alternating current. In principle, the conversion circuit according to this disclosure is usable separately from the fluid bath, for example in a vehicle, to charge the accumulator while driving. Such an application is not limited to cars, but also extends to other vehicles, such as electric trains, trams, wheelchairs, boats or aeroplanes, for instance.

Returning to the example of FIG. 2, the disclosed conversion circuit is provided with plugs 13,14, which constitute a supply terminal for supplying the alternating current from the socket. The supplied alternating current is first passed through an input stage, which in this example is comprised of a capacitor bank 15. The capacitor bank 15 comprises three capacitors 16 connected in parallel. In a variant (not shown) of the shown circuit the capacity of the capacitor bank 15 as a whole is adjustable by means of switches placed before the capacitors 15. By using the capacitor bank 15 with capacitors 16 of suitable capacity, no separate transformer is needed, and conferment of an almost completely reactive input impedance by the input stage upon the conversion circuit, when supplied from the mains (that is to say with alternating current having frequency in the range between 40 and 60 Hz), is also attained. Thus, current and voltage are almost 90° out of phase, as a result of which the apparent power consumed is almost equal to zero. The capacitor bank 15 makes the use of a separate transformer superfluous.

In other applications, the input impedance is always adjusted to the frequency of the power supply. For power current or current from a car dynamo, the frequency will be much higher, for example around 600 Hz. The input impedance of the disclosed conversion circuit is then again substantially reactive, through an appropriate choice of capacitors 16. The input stage is thus always adapted to the properties of the alternating feed current (which should also be taken to mean polyphase current), such that the input stage confers upon the circuit a substantially reactive input impedance in use.

After the input stage the current is only rectified by a bridge circuit 17 connected to the input stage. The rectified current is supplied to the electrolysis device 3 through connector clamps 18,19, attached to the positive and negative poles 7,8 of the electrolysis device 3. Because the conversion circuit is essentially comprised of the input stage with an almost purely reactive input impedance and the bridge circuit 17, a pulsating power is supplied to the electrolysis device 3.

It is observed that other rectifier circuits than the bridge circuit 17 shown in FIG. 2 are possible within the scope of this disclosure. In principle, a half-wave rectifier circuit is possible, but it is preferable, with a view to having the electrochemical process run faster and more efficiently, to use a full-wave rectifier circuit. The choice of rectifier circuit, in addition to the nature of the electrochemical process, determines whether and which harmonics of the alternating current frequency are passed. In an electrochemical process, only even harmonics are involved. This is an additional advantageous effect of the disclosed circuit, as odd harmonics are undesirable. The presence of the electrochemical process causes those components, usually responsible amongst others for problems such as overheating, to be eliminated. The harmonic components enhance the accelerating effect on the electrochemical process.

Returning to FIGS. 1A and 1B, the function of the fluid bath will now be described. Although vibrations in the electrolysis device can also be generated by other means, for example by means of a vibratory pad in the pedestal 9, pressure waves are preferably generated in the water 1, by means of an actuator 20 attached to the vessel 2. The actuator 20 could be a piezo actuator, but specially adapted loudspeakers driven by means of a magnet and solenoid are equally possible. Preferably, ultrasonic pressure waves are generated, preferably with a frequency of 20 kHz or more. The range above 25 kHz has proved to be particularly advantageous. It has been established experimentally that the effect of the pressure waves is largest between 20 kHz and 50 kHz. When using an electrolyte solution with water as component, the range of 38 46 kHz, and within that range 41 43 kHz in particular, is best. This is connected with the fact that the resonance frequency of water molecules lies at about 42 kHz.

The actuator generates a pressure wave with a plane wave front 30 propagating in a direction A towards the fluid container 4. The pressure wave impinges perpendicularly on a wall of the fluid container. This wall starts to vibrate and thus transmits the pressure wave to the electrolyte solution 6. The electrodes 5 also start to vibrate.

Through simultaneous driving of the actuator 29 and feed current through the disclosed conversion circuit, it is ensured that the electrolysis process in the electrolysis device 3 takes place quickly. The ion transport in the electrolyte solution 6 is accelerated, whilst outgassing of electrolysis products is accelerated by the pressure waves. By these means, the concentration of electrolysis product in solution is decreased, as a result of which the reaction in the electrolyte solution is accomplished more rapidly.

This disclosure is not confined to the embodiments described herein, which may be varied and still within the scope of the accompanying claims. In particular, the disclosed systems are not limited to the electrochemical processes mentioned. A galvanisation process for example, takes place more rapidly and more efficiently when use is made of the disclosed conversion circuit. 

1. A conversion circuit for converting an alternating current into a feed current for an electrochemical process, the conversion circuit comprising: at least one supply terminal for supplying an alternating feed current; a rectifier circuit for rectifying a supplied alternating feed current; and an output stage for supplying the rectified current to a device in which an electrochemical process is taking place; the conversion circuit further comprises an input stage connected between the supply terminals and/or rectifier circuit, wherein the input stage, when in use, confers upon the conversion circuit a substantially reactive input impedance.
 2. The conversion circuit according to claim 1, wherein the input stage comprises at least one capacitor connected in series between the supply terminals and the rectifier circuit.
 3. the conversion circuit according to claim 2, wherein the input stage comprises a capacitor bank, which comprises one or more capacitors connected in parallel.
 4. The conversion circuit according to claim 1, wherein the supply terminals are suitable for connection of the conversion circuit to the mains network.
 5. The conversion circuit according to claim 2, wherein the supply terminals are suitable for connection of the conversion circuit to the mains network.
 6. The conversion circuit according to claim 3, wherein the supply terminals are suitable for connection of the conversion circuit to the mains network.
 7. The conversion circuit according to claim 1, wherein the rectifier circuit comprises a full-wave rectifier circuit.
 8. The conversion circuit according to claim 2, wherein the rectifier circuit comprises a full-wave rectifier circuit.
 9. The conversion circuit according to claim 3, wherein the rectifier circuit comprises a full-wave rectifier circuit.
 10. The conversion circuit according to claim 4, wherein the rectifier circuit comprises a full-wave rectifier circuit.
 11. The conversion circuit according to claim 5, wherein the rectifier circuit comprises a full-wave rectifier circuit.
 12. The conversion circuit according to claim 6, wherein the rectifier circuit comprises a full-wave rectifier circuit.
 13. A system for carrying out an electrochemical process, comprising a device in which an electrochemical process is running and comprising a conversion circuit according to claim
 1. 14. The system according to claim 13, wherein the device in which the electrochemical process is taking place comprises a container for an electrolyte solution, wherein the system means for generating pressure waves in the electrolyte solution present in the container of the device.
 15. The system according to claim 13, further comprising a fluid bath, in which the container can be placed and provided with a means for generating pressure waves in the fluid bath when filled with fluid.
 16. A method of carrying out an electrochemical process, comprising using a conversion circuit according to claim
 1. 17. The method according to claim 16, further comprising having the electrochemical process take place in a container filled with an electrolyte solution, and generating pressure waves in the electrolyte solution present in the container.
 18. The method according to claim 17, further comprising generating pressure waves having a frequency in the range of 20 kHz and higher. 